Well, I guess I was wrong. One of the two SR227s I've replaced is still not working consistently. Moreover, I have a backboard issue with the pool saltwater system so I went and shut off the fuses to it. Now the one problematic AM466 at the distant garage seems to working again !!
Taking a closer look at the breaker box, I found the coupler I had installed years ago, a Leviton 6299. So I ordered an XBCR to replace that coupler seeing that the XBCR also adds a repeater and a 'signal booster' and 3 XPFs filters for wiring into the ones where I find to be noisy.
If this doesn't work, I guess I'll decide whether I want to lay out the cash for a XTBIIR and possibly a test meter, just to get a couple of lights to come on and off daily. Then again, if I throw in the extra $300 for both and EVERYTHING works, I'm inclined to get a CM15A as well and go crazy all over the house.